1. Field of the Invention
The present invention relates to spin motors for disk drives; more particularly, to low power and low height spin motors.
2. Description of the Related Art
Disk drive manufacturers and computer manufacturers usually establish standards for vibration and shock resistance for hard disk drives or (disk files) for data storage. The standards may be more stringent for disk drives intended for use in portable or lap-top computers or other harsh environments. Vibration and impact acceptance evaluations may be conducted by placing the drive being evaluated on a vibration table and subjecting the drive to vibrations of varying frequency and amplitude while the drive is operating. The performance of the drive is monitored to determine the frequency and amplitude of the applied vibrations which cause errors in seeking and/or track following. Seek and/or track following errors often result in "hesitations" in reading and/or writing data, and disk drives which are sensitive to applied vibrations of too low a frequency or amplitude may fail acceptance evaluations.
One effect of vibrations applied to a disk drive, and one cause of errors in seeking and/or track following is mechanical off-tracking, i.e., an unintended physical movement of the heads with respect to the disk(s). Mechanical off-tracking may be caused by movements of various structural components of the spin motor which cause the disk to tilt or wobble out of a plane normal to the axis of the motor spindle or by movements of other components of the disk drive with respect to the disk.
Among the criteria imposed on hard disk drives are vibration resistance, compactness, low weight, low power, and ease of manufacture--particularly reduced part count. All of these criteria are usually important to a computer manufacturer selecting a disk drive for use in a specific computer or for a specific type of application. Resistance to applied vibrations depends in part on the internal operating vibrations experienced by a spin motor because applied and internal vibrations may add under certain circumstances. Accordingly, improving the resistance of hard disk drives to applied vibrations is a continuing goal of disk drive manufacturers.
Spin motors for hard disk drives are conventionally brushless motors, and thus the armature of the motor will be referred to as the stator and the magnets will be referred to as the rotor. However, in a spin motor where the armature rotates and brushes are used to contact the armature, the armature would be referred to the rotor and the magnets would be referred to as the stator.